Strand treatment method



1970 R. K. STANLEY Q 3,536,807

STRAND TREATMENT METHOD Original Filed Aug. 5, 1965 mvavme ROBERT K. STANLEY By M U rw United States Patent Us. or. 264-282 1 Claim ABSTRACT OF THE DISCLOSURE A process of drawing and crimping textile strands is provided wherein a strand is drawn to increased length while being simultaneously snubbed and cooled at one side, whereupon the strand then or thereafter assumes a crimped configuration.

Reference is made to my copending application, Ser. No. 476,933 filed Aug. 3, 1965, upon which the present application is based. Reference is also made to my related copending applications filed as continuations-in-part thereof: Ser. No. 511,929 filed Dec. 6, 1965, now Pat. 3,374,302; and Ser. No. 687,391 filed Dec. 1, 1967.

This invention relates to drawing of molecularly orientable textile strands to increased length and thereby orienting them, and concerns also the crimping of such textile strands. Such a strand is pulled slidably over a snubbing surface, and the side in contact with the snubbing surface is cooled thereby, whereupon the strand acquires an extended length and a bulky or crimped configuration.

Many textile strands, especially those composed of synthetic organic polymers of linear structure, are molecularly orientable by a procedure of extending the strand beyond its elastic limit or drawing it, whereupon the strand does not break but attains a stable extended length by virtue of longitudinal alignment and possibly slippage of the component polymeric molecules. Such procedure usually involves pulling the strand about a solid snubbing surface, most often cylindrical, and frequently involves heating the strand or the snubbing surface or both.

A primary object of the present invention is improvement in strand-drawing. 1

Another object is provision of crimped strands by way of a novel drawing technique.

A further object is provision of a draw-crimping process and apparatus for practicing it.

Other objects of this invention, together with means and methods for attaining the various objects, will be apparent from the following description and the accompanying diagrams.

FIG. 1 is a representation, partly in elevation and partly in schematic form, of apparatus according to the present invention; and

FIG. 2 is a similar view on a reduced scale, of further apparatus according to this invention, and of crimped strand produced thereby.

In general, the objects of the present invention are accomplished by pulling a molecularly orientable textile strand over a snubbing surface to draw it to increased length and thereby orient it, and simultaneously cooling the strand while in contact therewith. Upon subsequent relaxation from tension, with or without the aid of heat, the strand assumes a crimped configuration.

FIG. 1 shows strand 11, a molecularly orientable type, being fed by pair of feed rolls 12, 13 toward the upper right, past heater 14 and to snubbing member 15, which 3,536,807 Patented Oct. 27, 1970 has semicylindrical snubbing surface 16. The strand is pulled past the heater and over the snubbing surface, and thereby extended (after which it is denoted as 11'), by pair of draw rolls 17, 18. Block 19 denotes drive means for the rolls by means of suitable drive linkages (indicated in broken lines): 19a to feed roll '13, 19b to draw roll 17, and 19c to a roll discussed hereinafter. The drive means comprises either an engine or an electric motor (not shown) together with suitable gearing (also not shown) so that the respective pairs of rolls can be driven at any desired angular speeds and any desired speed ratio. The second roll in each pair may be undriven except by contact with the driven roll and the strand passing through the roll nip, or both rolls in any pair may be driven alike (but in opposite directions). The draw rolls are driven at a greater surface speed than the feed rolls, preferably several times as great, the actual speed ratio depending upon the drawability of the strand composition and the desired degree of draw to be accomplished.

Snubbing member 15 is provided with conduits 21 and 23, shown with arrows leading respectively to and from the snubbing member, which is hollow (as indicated in broken lines) to interconnect them, and respectively from and to block 25, which represents circulation-inducing means and heat sink. Thus, where the circulating material is a refrigerant fluid, for example, the conduits and the interconnection thereof in the snubbing member comprise the cooling coil, the rest of a conventional refrigerator being represented by block 2-5, and enlarged portion 22 of the interconnection in the interior of the snubbing member representing a plenum chamber, preferably supplied with fins to the body of the member for ready heatexchange therewith. Alternatively, conduits 21 and 23 may be simply electrical conductors (the arrows representing electrical current flow therein), in which event block 25 represents a DC. generator, battery, or equivalent source, and enlarged portion 22 in the snubbing member represents a thermoelectric device (e.g., a Peltier junction or group thereof) adapted to produce a cooling effect upon current flow therethrough in the indicated direction, the selection of which is well within the capability of a person skilled in the art.

FIG. 2 shows (on a reduced scale) drawn strand 11 proceeding to the right past heater 27 to pair of strandforwarding rolls 28, 29 driven through linkage 19c (indicated in broken lines) at a usually intermediate surface speed suflicient to maintain in the strand at least some of the tension imparted by the strand-drawing rolls despite any change in length induced by heater 27 when on. This remaining tension, which may be only sufiicient to prevent slack in the strand, is released as the roll nip releases the strand (then denoted as 11") into relaxed crimped configuration, which is shown somewhat stylized. If desired, the strand-forwarding rolls may be omitted and the tension be released at the nip of the strand-drawing rolls. Also, if desired the strand-feeding rolls may be replaced by equivalent strand-restraining means effective to ensure adequate contact between the strand and the surface of the snubbing member as the strand-drawing rolls pull the strand thereover. The relaxation step, which induces stress relief in the strand, may be repeated, if desired, with or without variation therein.

Use of either or both of heaters 14 and 27 may be dispensed with as may be desired. Heater 14, which is a preheater to facilitate drawing as is desirable with some strand compositions, may be replaced upon providing one or both of feed rolls 12, 13 with internal heating means, such as that shown and described for the feed rolls of a stulfer crimper in my Pat. 3,111,740. Alternatively, with strands of readily drawable compositions, heater 14 may be removed without such modification of the feed rolls (or simply be left in place but not turned on), as the friction of the strand against snubbing surface 16 and the intermolecular friction engendered as the strand begins to draw will induce a heating of the strand. Of course, the cooled snubbing member acts to remove heat of whatever origin from the drawing or drawn strand; however, unlike the preferred heaters, it does not act uniformly on the strand but contacts it along one side only. Heater 27 is used to heat-relax the drawn strand wherever the latent crimp is not developed to the extent desired upon simply relaxing the strand by releasing it from tension. Where not required it can be removed or left in place turned off. A heat-relaxation after treatment may be employed instead of or in addition to heat-relaxation by heater 27. Both heaters 14 and 27 may be of any suitable design, such as an enclosure supplied with radiant energy, steam, or other means of heat-transfer, or simply a heated block over which the strand travels in heat-conductive contact.

Snubbing member 15, and particularly snubbing surface 16 thereof, is composed of any suitable hard material having suitably high heat-conductivity characteristics, usually a metal or alloy thereof. Conventional steel draw pins often are suitable for such member and may be cut in half longitudinally and hollowed if necessary. A semicylindrical snubbing surface is most convenient, as the strand does not wrap one or more turns about the member as is customary in conventional drawing operations with cylindrical draw pins but passes thereover through a preferred angle of about a radian of arc, or at least about a half radian and at most about two radians. Of course, a non-arcuate curved surface may be used, if desired. In either event the average radius of curvature of the snubbing member should be large with respect to the filamentary diameter of the strand, and for the purposes of this invention large means a minimum ratio of about one hundred times. For most purposes the snubbing member will be selected to have a radius of not less than about one centimeter nor more than about ten centimeters.

The strand may be a monofilament or multifilament and may range in size from as small as one or two to fifteen or more denier per filament. In the instance of multifilament strands the total denier may be in the hundreds or even the thousands. In the instance of multifilament each component filament of the strand should have a diameter of at most about one one-hundredth of the radius of curvature of the snubbing surface. In the processing of large bundles of filaments it is preferred to spread them laterally by any suitable means to ensure that the individual filaments are gripped securely by the rolls and are brought into relatively good heat-exchanging relation to the heaters (when used) and the snubbing member. The removal of heat from each filament of the strand by means of the snubbing member during drawing induces a transverse non-uniformity therein, which although only imperfectly understood induces a most satisfactory crimp, the full extent of which becomes apparent only upon subsequent relaxation of the strand, performed one or more times.

Suitable temperatures or ranges thereof for the snubbing member and the preheater, if used, depend upon the strand composition, period of exposure thereto, and heattransfer characteristics. For example, an undrawn 6-nylon strand of forty four hundred total denier and sixty-eight filaments was fed at two and one half meters per minute and drawn at a rate of about ten meters per minute (4X draw) without preheating, through slightly more than 30 of are over the surface of a cylindrical snubbing member having a diameter of about ten centimeters and maintained at a temperature of 20 to 25 C. It is estimated that the drawing momentarily increased the strand temperature to about 6 5 to C. but that it was reduced by the cool snubbing pin to not more than 40 C. Upon release of tension the individual filaments in the strand assumed a coiled or curly crimped configuration, which was intensified by after treatment at a temperature of about C.

Articles made by knitting, weaving, or otherwise fabricating such strands, with or without addition of other strands or materials, exhibit desirable characteristics of cling, cover, elasticity, and the like. The invention provides such strands by a rapid, readily controlled, and inexpensive technique. It may be incorporated in the manufacturing line of a plant in which synthetic strands of molecularly orientable compositions are extruded from melts or solutions thereof. Although a preferred apparatus embodiment has been illustrated and described, and certain modifications suggested, other modifications may be made therein while retaining at least some of the benefits of the present invention, which itself is defined only in the following claim.

The claimed invention:

-1. In treatment of a textile strand adapted to be drawn to increased length, the steps of drawing the strand to increased length, while snubbing one side of the strand at a curvilinear portion of its path to localize drawing thereat, and providing in the strand at that snubbing location a temperature differential extending transversely from a relatively low temperature on the snubbed side of the strand to a relatively high temperature on the opposite side thereof.

References Cited UNITED STATES PATENTS 2,974,391 3/1961 Speakman et a1. 28-] 3,113,366 12/1963 Taylor 28-72 3,233,019 2/ 1966 Adams v 264-210 3,302,385 2/ 1967 Ruddell et al 264-168 3,347,036 10/1967 Daniel 264168 3,358,344 12/1967 Daniel 264-168 3,358,345 12/1967 Daniel 28-72 3,374,302 3/ 1968 Stanley 264-168 3,374,514 3/ 1968 McClure 264-468 FOREIGN PATENTS 328,312 1930 Great Britain. 558,297 1945 Great Britain.

ROBERT F. WHITE, Primary Examiner R. R. KUCIA, Assistant Examiner US. Cl. X.R. 264-168, 29.2 

